SQL
So for a customer:
Name like '%Dave%'
Will give you anyone with "Dave" in their name.
FirstName = 'Dave'
Will give you all the Dave's, but not the Davea's.
Or for an Activity:
DueDateStart > '2012-05-31'
Would give you all activities after midnight (UTC time) of May 31st.
It's obviously on our todo list to make a user interface that allows non-SQL'rs to build the scripts visually.
BTW - did you get my tweet about the Gmail Gadget? We're accepting beta requests - you'll love it.
Paul